Occasionally, electric circuits are subjected to inadvertent high amperage loads which have the capability of damaging the circuit and devices connected to it, and which not infrequently produce sufficient heat to result in fires. To avoid such possibilities, overload protection devices, including circuit breakers, fuses, and the like which either fail, or "trip" when subjected to overload conditions, have long been employed. In those instances where fuses are used to protect the circuit, several systems for incorporating the fuses into the circuit are commonly used. One such system involves the placement of a group of fuses, protecting a number of circuits, at a single location or "fuse block". While the use of a fuse block has certain advantages, including the ability to examine the condition of fuses in multiple circuit, simultaneously, its use has the significant disadvantage of requiring part of each of the circuits protected to pass through the fuse block. Such requirement frequently necessitates long runs of wire from the area where the electric power provided by the circuit is used, to a fuse block remote from such area, often a time-consuming and expensive undertaking.
A different system of fuse protection involves the use of the so-called "in-line" fuse, which allows the fuse to be located at any point in the circuit, rather than requiring location at a single point such as a fuse block. In-line fuses are available in several forms, one commonly used being that of the ferrule type, a glass cylinder with metal ends having a fusable link connected therebetween, typically held in a "bayonet-type" holder fitted with a wire at each end which is spliced into the circuit line. Unfortunately, bayonet-type holders are frequently difficult to open when a damaged fuse needs to be replaced. In addition, the wires connected to the bayonet holder must each be spliced into the line, a time consuming operation. Furthermore, the multiple connections entailed in using bayonet holders, involving both the connection of the wires to the metal ends of the holders, as well as the connections required to splice the wires into the circuit wire, commonly produces appreciable and undesirable electrical resistance in the circuit. While use has also been made of holders designed to receive "doubled-bladed" fuses, such holders also have been connected to wires which require splicing into the circuit line, as in the case of the bayonet holders, again creating the potential for high resistance circuits.